Pantograph and motor control system



Patented Feb. 17, 1948 PANTOGRAPH AND MOTOR CONTROL SYSTEM William M.Hutchison, Pittsburgh, Pa., assignor.

to Westinghouse Electric Corporation, East Pittsburgh, Pa., acorporation of Pennsylvania Application March 18, 1944, Serial No.527,127

2 Claims. 1

My invention relates. generally, to control systems and apparatustherefor, and, more particularly, to systems and apparatus forcontrolling the operation of, and protecting the electrical equipmenton, electric railway vehicles.

A circuit breaker is provided on electric railway vehicles of certaintypes to disconnect the electrical apparatus on the vehicle from thepantograph collector which engages the trolley conductor. In view of thelimited space on such vehicles, the circuit breaker usually does nothave sufiicient rupturing capacity to interrupt the current which flowsin case of a short circuit in the electrical apparatus. Muchconsequential damage may result if the circuit breaker fails in theevent of an overload. Therefore, it has been the practice to energizethe operating coil of the circuit breaker through a time delay relaywhich functions to cause the breaker to open upon over-' load only aftersufiicient time has elapsed to permit the substation circuit breakers toclear the faults. When a fault occurs on the system, the circuitbreakers in the nearest substations are opened, thereby isolating thesection in which the fault is located.

The foregoing system of operation has the disadvantage inherent in timedelay devices which are subject to variation in their timing even withcareful maintenance, that is, it requires the maintenance of adiiierential in time between operation of the substation breakers andthe relay. Furthermore, no protection is provided against the loweringofthe pantograph by the operator during the interval that a faultexists, which might result in damage to the pantograph and seriousburning of the trolley wire,

Accordingly, one object of my invention is to prevent the circuitbreaker on a railway vehicle from interrupting an abnormal current.

Another object of my invention is to prevent the lowering of thepantograph on an electric railway vehicle while an abnormal current isflowing in the power circuit or apparatus thereof, or some otherpredetermined electrical condition of said circuit or apparatus exists.

A further object of my invention is to provide a protective relaycapable of performing the functions of a conventionalpantograph-lowering relay and a circuit breaker operating relay withouthaving the disadvantage of a time delay feature.

A more general object of my invention is to provide such a protectiverelay which shall be simple and efficient in operation and which may beeconomically manufactured and installed.

Other objects of my invention will be explained 2 fully hereinafter orwill be apparent to those skilled in the art.

In accordance with one embodiment of my invention, a relay responsive tothe current in the apparatus on a railway vehicle is provided with anarmature on which two sets of contacts are mounted and which operatesagainst a calibrating spring, and also with tWo sets of auxiliarycontacts which are normally held closed by'a latchon the relay armature.Operation of the armature by a predetermined current in the actu atingcoil releases the latch'and causes the auxiliary contacts to assume thetripped position until they are reset manually. The relay contacts areso connected in the control system that the vehicle circuit breakercannot open in case of a heavy fault current until after a substationbreaker has cleared the fault and the pantograph cannot be lowered untilthe trolley wire is deenergized by operation of the substation breaker.

For a fuller understanding of the nature and objects of my invention,reference may be had to the following detailed description, taken inconjunction with the accompanying drawing, in which the single figure isa diagrammatic view of a control system and protective relay embodyingmy invention.

Referring to the drawing, the system shown therein comprises a loadcircuit II), which includes a transformer I l a motor I 2 and the usualcontrol equipment l3 for controlling the operation of the motor l2, anda circuit breaker M for connecting the transformer H to a pantographcollector l5 which engage a trolley conductor I E. The pantograph 15 maybe of the usual type which is raised by a spring l6 and lowered by apiston ll disposed in a cylinder l8. The admission of air to thecylinder I8 from an air reservoir l9 may be controlled by a magnet valve2| which is actuated by a solenoid 22.

In accordance with the usual practice in electric railway systems, theoverhead trolley system is divided into sections and the varioussections are energized from suitable sources of power disposed insubstations which are located throughout the system. In the present casethe trolleyconductor It may be considered as representing one section ofthe overhead trolley system, and it is energized by a. suitablegenerator 23 which is connected to the trolley conductor I 6 through acircuit breaker 24. The circuit breaker 24 is provided with an overloadtripping device 25 for I automatically opening the circuit breaker incase 24 is located in a substation and has sufiicient rupturing capacityto interrupt the current under short-circuit conditions, while thebreaker M, which is located on the railway vehicle, is not designed forinterrupting a current of the magnitude encountered under short-circuitconditions, Furthermore, as explained hereinbefore, the pantograph mustnot be lowered from the trolley conductor "5 while carrying abnormalcurrent.

In order to prevent the circuit breaker l4 on the vehicle fromattempting to interrupt the power circuit under abnormal conditions, aswell as to prevent the pantograph from being lowered while an abnormalcurrent is flowing, an electromagnetic relay 26 is provided. As shown,the relay 26 comprises a core 21 upon which is mounted an operating coil28 which is energized from a current transformer 29 connected in thecircuit for the power transformer H, and a pivotally mounted armature 3|which carries two sets of contact members 32 and 33. The armature 3| isbiased to the open position by a calibratingspring 34.

In addition to the contact members 32 and 33, the relay 2B is providedwith auxiliary contact members 35 and 36 which are carried by apivotally mounted contact arm 31 and are disposed to engage fixedcontact members 38 and 39, respectively, when the relay is in the normalor untripped position. The contact arm 31 is retained in the normalposition shown in the drawing by a latch arm 4| carried'by the armature3| and is biased to the tripped position by a spring 42. When thecontact arm 31 is in the tripped position, the contact members 35 and 36are disengaged from the contact members 38 and 39, respectively, and thecontact member 36 engages a fixed contact member 43.

Amanually operable control switch CS is provided to enable the operatorof the vehicle to control the operation of the circuit breaker l4 andthe lowering of the pantograph i5 under normal operating conditions. Theswitch CS may be located in the operators cab in accordance with theusual practice.

In order that the functioning of the foregoing apparatus may be moreclearly understood, the operation of the system will now be described inmore detail. When the control switch CS and the relay 26 are in thepositions shown in the drawing, the actuating coil for the circuitbreaker I4 is energized through a circuit which may be traced frompositive through a segment 44 of the switch CS, conductor 45, contactmembers 38 and 35 of the relay 26, conductor 46 and the actuating coil41 to negative.

At this timethe pantograph 5 is raised by the spring I6 since theactuating coil 22 of the magnet valve 2| is deenergized and the valveprevents air from being admitted to the cylinder 8. If the operatordesires to open the circuit breaker l4 and lower the pantograph [5, theswitch CS is actuated to a position which deenergizes the conductor 45and energizes a conductor 48. When the conductor 45 is deenergized theactuating coil 41 of the circuit breaker I4 is deenergized therebyopening the circuit breaker. When the conductor 48 is energized, theactuating coil 22 of the magnet valve 2| is energized through a circuitwhich extends from the conductor 48 through contact members 39 and 36 ofthe relay 26, a conductor 43, contact members 32 of the relay 26 and theactuating coil 22 to negative. When-the coil 22 is energized the 4magnet valve 2| is operated to admit air to the cylinder l8, therebylowering the pantograph l5. In the event of a short circuit in theelectrical apparatus, or other condition which causes an abnormalcurrent to flow through the current transformer 29, the current in thecoil 28 of the relay 26 causes the armature 3| to be pulled downwardlyagainst the restraining spring 34. The initial movement of the armature3| interrupts the circuit through the contact members 32 to the coil 22of the magnet valve 2|, thereby preventing energization of the coil 22to lower the pantograph l5, and establishes a circuit for the closingcoil 41 of the breaker l4 through the contact member 33 which isactuated into engagement with a fixed contact member 5|. Further travelof the armature disengages the latch arm 4| from the contact arm 31,thereby permitting the contact arm to be actuated to the trippedposition by the spring 42.

At'this time the circuit to the magnet coil 22 is interrupted by theopening of the contact members 36 and 39 of the relay, therebypreventing the lowering of the pantograph even though the operatoractuates the switch OS to the down" position. Furthermore, the circuitbreaker M is held closed since its operating coil 41 is kept energizedthrough a circuit which extends from positive through the contactmembers 5| and 33 of the relay 26, a conductor 52, the contact member35, conductor 46 and the actuating coil 41 to negative.

When the fault is cleared by the opening of the substation circuitbreaker 24, the current in the relay magnet coil 28 is reduced to zeroand the armature 3| is biased to the deenergized position by the spring34. However, the auxiliary contacts 35 and 36 remain in the trippedposition. 7

Under the foregoing conditions, the coil 22 of the magnet valve 2| isenergized through a circuit which extends from positive through contactmembers 43 and. 36 of the relay 26, the conductor 49, contact members32, and the actuating coil 22 to negative. Furthermore, the energizingcircuit for the actuating coil 41 of the circuit breaker I4 isinterrupted by the disengagement of the contact member 33 from thecontact member 5| of the relay 25. In this manner the pantograph I5 islowered and the circuit breaker I4 is opened after the fault has beencleared by the substation breaker. I order to reestablish normaloperation, the relay 26 may be reset manually to restore the auxiliarycontacts to the latched position.

With the foregoing system of operation, all abnormal currents areinterrupted by the substation breaker or breakers, thereby eliminatingthe danger of interrupting such currents by the circuit breaker locatedon the vehicle. Furthermore, the pantograph I5 cannot be lowered whilean abnormal current is flowing but is automatically lowered after thefault is cleared, thereby isolating the vehicle to permit the fault tobe located and the trouble corrected.

From the foregoing description, it is apparent that I have provided asingle relay which combines the features of a pantograph-lowering relayand of a circuit breaker operating relay in one device. Furthermore, thepresent relay does not have the disadvantage of requiring a time delaydevice to control the sequence of operation of its contact memberswhich, in the present device, automatically operate in the desiredsequence.

Since numerous changes may be made in the for engaging a trolleyconductor, in combination,

a load circuit, a circuit breaker for connecting the load circuit to thepantograph, means for lowering the pantograph, manually operable meansfor normally controlling the operation of said circuit breaker and saidpantograph-lowering means, and relay means responsive to the current insaid load circuit and having contact members thereon operable insequential relation for controlling the operation of said circuitbreaker and said pantograph-lowering means independently of saidmanually operable means, the control for the circuit breaker beingtransferred from one set of said relay contact members to another duringthe operation of the relay.

2. In a system for controlling the operation of an electric vehiclehaving a pantograph collector for engaging a trolley conductor, incombination, a load circuit, a circuit breaker for connecting the loadcircuit to the pantograph, means for lowering the pantograph, manuallyoperable means for normally controlling the operation of said circuitbreaker and said pantograph-lowering means, and a relay responsive tothe current in said load circuit and having contact members thereonoperable in sequential relation for preventing the opening of saidcircuit breaker and the lowering of said pantograph while the current inthe load circuit exceeds a predetermined amount and for causing theopening of the circuit breaker and the lowering of the pantograph aftersaid current is reduced below a predeter mined amount, the control forthe circuit breaker being transferred from one set of said relay contactmembers to another during the operation of the relay.

WILLIAM M. HUTCHISON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,159,936 Harris Nov. 9, 19151,654,316 Wickerham Dec. 27, 1927 1,682,432 Smith Aug. 28, 19281,794,93? Wittaker et a1. Mar. 3, 1931 2,059,069;v Tritle et a1 Oct. 27,1936 2,106,84 Harder et a1 Feb. 1, 1938 2,289,182 Dickinson July 7, 1942

